Esterification reactions for the production of acrylic esters are well known in the art. The esterification generally involves the reaction of an (meth)acrylic acid and alcohol having 4 or more carbon atoms, in the presence of a strong acid catalyst to produce the corresponding desired ester. U.S. Pat. No. 5,386,052, herein incorporated by reference in its entirety, describes the reaction generally, and claims a process for producing acrylic or methacrylic esters. Examples of acids employed in the reaction process include, but are not limited to sulfuric acid, p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, naphthenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, and the like. These strong acids must be removed from the reaction liquid after the reaction is completed. The acid then must be disposed. Currently, all methods of disposal have an environmental impact. One method is to dilute the acid with water. Thereafter the water must be treated and disposed. Accordingly, the acid must also be separated from the water and disposed, usually by incineration, or recovered.
U.S. '052 also describes a method for the removal of the acid whereby the reaction liquid (containing a predominantly desired ester product which is water insoluble) is extracted with water, separated from the aqueous solution containing the acid catalyst, and recycling the aqueous solution.
Also described in U.S. '052 is a method for removing the strong acid in which the reaction liquid is treated with an aqueous alkaline solution for neutralization (Japanese Laid-Open Patent Publications Nos. 243046/1986, 34965/1991 and 230240/1992). According to this method, a large amount of alkali is needed for effecting a sufficient neutralization. Moreover, it is very difficult to separate and recover the acid catalyst and unreacted acrylic or methacrylic acid from the aqueous alkaline solution after the treatment and, therefore, the aqueous alkaline solution must be disposed as a waste after the treatment. A drawback of this method is the production of a large amount of waste water which contains a high concentration of potentially harmful organic acid salts.
Due to the above drawbacks, it is desirable to remove as much sulfur containing compounds from process steams as possible, so as to minimize environmental impact(s). It is also desirable to recover and reuse the acid catalyst so as to reduce the overall costs involved in the esterification reaction, as well as reduce the labor and expense involved in any acid disposal.